1. Technical Field
The present disclosure relates to a stopping control apparatus for a vehicle, e.g., a motor vehicle.
2. Description of the Related Art
When a vehicle, e.g., a motor vehicle, stops on a slope, the stop state of the vehicle needs to be maintained even after the stop of the vehicle. For example, in Japanese Patent Application Laid-open No. 2015-30293, there is disclosed a stopping control apparatus configured to carry out hill hold control of applying braking forces to wheels when a hill hold condition is satisfied, and to, when the hill hold control is released, switch a gear-type transmission to a parking lock state before the release. With the stopping control apparatus of this type, compared to a case where the transmission is not switched to the parking lock state before the hill hold control is released, a fear for a movement of the vehicle after the stop on the slope can be reduced.
In general, the switching of the transmission to the parking lock state is achieved by engaging a lock pawl to a gear for locking in the transmission, thereby blocking a rotation of the gear. Backlashes are provided in meshing portions of a plurality of gears in the transmission. Thus, even when the transmission is switched to the parking lock state, the gears meshing with each other on a wheel side with respect to the gear for locking can thus relatively rotate by a gap amount of the backlash.
Therefore, in the stopping control apparatus disclosed in Japanese Patent Application Laid-open No. 2015-30293, when the transmission is switched into the parking lock state, the hill hold control is released, and the braking forces are thus not applied to the wheels, resulting in a state where the retention of the rotation of the wheels by the braking forces is released. A force in a slope descending direction caused by the gravity acts on a vehicle body of the vehicle. Thus, an output shaft of the transmission slightly rotates as a result of the relative rotations of the plurality of gears in the transmission. As a result, the rotations of the wheels may cause the vehicle to slightly move towards the slop descending direction.
Speeds of the fast relative rotations of the plurality of gears increase as an inclination angle of the slope increases. Thus, when the inclination angle of the slope is large, the plurality of gears relatively rotate fast, and a so-called gear rattle and a shock may thus be generated by hard collisions between teeth of the gears meshing with each other.
When the braking forces applied to the wheels are decreased at a low rate at the time of hill hold control release in order to prevent generation of the gear rattle and the shock, a period until the hill hold control release is completed becomes excessively long.